Low toxicity tobacco



United States Patent O LOW TOXICITY TOBACCO Walter Rosenthal, 110 W. 96th St., New York '25, N.Y., gllldloxllm Staige Davis, Jr., 135 E. 65th St., New York No Drawing. Filed Mar. 27, '19'57, Ser. No. 650,063

6 Claims. (Cl. 131-17) The present invention relates to smoking tobacco which when burned produces smoke having a reduced nicotine and carcinogenic tar content and, further, to a method for the production of such tobacco.

The medical profession and public have been concerned in recent years over the high incidence of cardiovascular disease and respiratory cancer among tobacco smokers. Since it has been maintained by some authorities that these .conditions are caused by the nicotine and tars present in tobacco smoke it has become common practice to provide cigarettes and other smoking articles with filters designed to remove at least a part of the nicotine and tars from the smoke inhaled by smokers. The more fundamental expedient of eliminating or materially reducing the nicotine content of tobacco itself has also been employed. Neither of these methods of reducing the amount of nicotine and tars inhaled by smokers has been entirely satisfactory, however, since both practices alter the flavor and aroma of the tobacco and thus reduce smoking pleasure.

A method for the treatment of tobacco has now been discovered which materially reduces the amount of nicotine and carcinogenic tars volatilized into the tobacco smoke without, however, adversely affecting the taste or aroma of the treated tobacco or reducing the smokers pleasure. The new method consists of exposing tobacco, whether in the form of the crude leaf, cased leaf, cased and cut smoking tobacco or finished smoking articles such as cigars and cigarettes, either loose or packaged, to the action of certain lower alkyl halides under mild reaction conditions. The term halide is intended to include iodine, bromine and chlorine. Mild reaction conditions, i.e., normal or slightly elevated temperatures and pressures and minimum effective exposure times, are employed to avoid possible damage to the delicate flavor and aroma of the treated tobacco. 1

Although it has not been definitely established, the reduced nicotine and tar content of the smoke from tobacco treated according to the present invention is presumably due to the reaction of the lower alkyl halide treating agents with the nicotine content of the tobacco to form one or more non-volatile, combustible compounds which, when the tobacco is burned, are converted to harmless combustion products, thus preventing volatilization of nicotine and carcinogenic tars into the smoke. The alkyl halide treating agents react with the nicotine content of the treated tobacco largely according to the following equation:

C Hz-C H: (i? H B 3 Ha H O H2 ll N (7H5 N (3H Alkyl Nicotine Alkyl nicotim'um halide halide in which R represents a lower alkyl group having. not

Patented May 23, 1961 more than two carbon atoms, i.e., a methyl or ethyl group, and X represents iodine, bromine or chlorine. It is probable, however, that some reaction also takes place between the alkyl halide treating agent and the nitrogen atom in the N-methylpyrrolidine ring (marked B in the above formula) of the nicotine molecule. Therefore, tobacco treated according to the present invention may contain a mixture of nicotine-alkyl halide reaction products including compounds in which the alkyl halide addition has occurred on either one or on both of the nitrogen atoms in the nicotine molecule.

The specific alkyl halide treating agents useful in the treatment of tobacco according to the invention to prevent the volatilization of nicotine as such into tobacco smoke are listed in the table below.

These agents are employed in the vapor or gaseous phase to assure intimate contact with the tobacco to be treated while minimizing the possibility of aifecting the flavor of the product. The lower boiling treating agents, which are preferred in general, can be cooled and liquified for ease in handling prior to use and then vaporized in the presence of the tobacco to be treated. The higher boiling treating agents, while useful are not preferred since relatively high treatment temperatures are required to maintain them in the vapor phase. Further, it is more diflicult to remove excess treating agent from the treated tobacco when the higher boiling compounds are employed.

The type of halogen present in the treating agent also affects .its usefulness. The iodides, although useful in the invention and more reactive than the bromides or chlorides, are not recommended since it has been observed that tobacco treated with these compounds has a tendency, when burned, to release small amounts of free iodine into the smoke. The chlorides are the least reactive of the three useful halides and therefore require relatively longer reaction times and higher reaction temperatures which tend to affect the flavor of the treated tobacco. The bromides and particularly methyl bromide are preferred, therefore, since they are more reactive than the chlorides and yet are not subject to the noted disadvantages of the iodides. Methyl chloride, which is otherwise a desirable treating agent, is somewhat disadvantageous economically due to its high vapor pressure which necessitates the use of relatively expensive pressure resistant reaction vessels.

The new method is normally practiced by introducing the lower alkyl halide treating agent to a closed reaction vessel containing tobacco to be treated and maintaining the vessel at normal or elevated temperatures for suflicient time to insure substantially complete treatment of the tobacco. Many factors such as the reactivityof the treating agent, reaction temperature and pressure, concentration and amount of treating agent employed and the nicotine content of the tobacco, influence the exposure or reaction time required for satisfactory treatment. In general, however, exposure times varying from about two hours or less to 48 hours are employed and in the majority of cases a reaction time of about 4 to about 20 hours is suflicient.

Suitable reaction temperatures vary from the lowest temperature'at which an appreciable reaction rate can be obtained with the particular treating agent up to the temperature at whichthe flavor of the tobacco is "seriously affected. Since there is nothing to be gained in most cases from employing temperatures lower than normal or ambient temperatures, the upper temperature limit is the important one. It has been found that about 60 C.isthe practical upper limit of reaction temperature, since higher temperatures, particularly on long exposure, tend to afiect the flavor of the tobacco. The preferred reaction temperatures are about 45 to about 50 sinceithese can be employed with safety and yet are sufliciently high to give a satisfactory reaction 'rate with the preferred treating agents described above. In some cases, for example, where a relatively high-boiling treating a gent such as methyl or ethyl iodide isrto be employed temperatures ranging up to about 100 C. can be used. Such reaction temperatures are not, however, generally recommended.

The amount of lower alkyl halide employed in the present invention varies with the nicotine content of the tobacco to be treated. Since complete elimination of nicotine from tobacco smoke is not required to realize substantial benefits from the invention it is not essential that all of the nicotine in the tobacco be reacted with treating agent. For this reason it is unnecessary to employ the stoichiometric quantitylone mole of treating agent per mole of nicotine) of treating agent in every instance. However, since other factors such as the reaction temperature and exposure time also influence the completeness of the treatment it is usually desirable to employ at least one mole of treating agent for each mole of nicotine present in the sample to be treated. It has been found, moreover, that improved results are obtained when an excess of treating agent is employed, e.g., up to about 1.3 moles of treating agent per mole of nicotine. With the preferred methyl bromide treating agent the use of from 1.1 to 1.2 moles of treating agent per mole of nicotine in the tobacco to be treated is recommended. Large excesses of treating agent should be avoided, however, since they may affect the flavor of the tobacco.

The halide treating agents can be employed individually or in mixtures with each other or they can be diluted for use with any suitable inert gas.

The invention will be illustrated in greater detail by the following specific examples:

Example I A quantity of cased and cut smoking tobacco suitable for cigarette manufacture is analyzed for nicotine. A 2-lb. sample of the tobacco containing 2.8% of nicotine by weight, is packed into a glass container of suflicient volume to just accommodate the charge. Approximately 17.3 grams cc.) of methyl b'ror'nide (about 16% excess of stoichiometric) is cooled to about 20 C. in brine and the test tube containing the treating agent is introduced to the tobacco-packed container. The mouth of the glass container is then sealed quickly 'byfusion in a flame before the methyl bromide vaporizes from the test tube. The sealed container is then placed in a water bath and heated to about 45 C. for 24 hours. The container is then removed from the bath, cooled and opened. The

The treated tobacco is fashioned into cigarettes. smoke from these regulator size (7 cm.) cigarettes contains 0.81 mg. of nicotine by weight as compared to a nicotine content of 2.55 mg. for the smoke from similar cigarettes made from untreated tobacco taken from the same lot as the test sample. The method of the invention achieved a 68% reduction in the nicotine content of the tobacco smoke.

Example ll Ten grams of cigarette tobacco is placed in a glasstube and about 0.3 gram of methyl iodide is' added. The

The treatment of Example II can also be carried out employing 10 grams of cigarette tobacco, 0.4 gram of ethyl iodide and a boiling water bath. The tobacco smoke contains about 2.4 mg. of nicotine by weight prior to treatment and 1.1 mg. after treatment; therefore the method of the present invention reduces the nicotine content by about 54%.

Example IV A commercial scale treatment can be conducted by placing about 200 lbs. of crude tobacco leaf having a nicotine content of about 2.5% by Weight in a low pressure water-jacketed autoclave and adding 2.5 lbs. of cooled ethyl chloride. The autoclave can then be heated to about 55 C. and maintained at that temperature for about 24 hours. The resulting product, when manufactured into cigarettes, would be found to be substan-.

tially unaltered in flavor but when burned would produce a smoke having a substantially reduced nicotine content. I

Although it is possible in many cases, by adjusting the reaction conditions within the limits set out above,

I to reduce the nicotine content of the smoke of the treated tobacco to substantially 'z'ero, it is generally undesirable. to do so since the resulting product may have a flat taste unacceptable to many smokers. Therefore, since it is not necessary to completely eliminate nicotine from tobacco smoke to obtain substantial advantage from the present invention, it is preferred to adjust the reaction conditions to remove only about 40 to or preferably about 50 to 70% of the nicotine in tobacco smoke. Of course, any substantial reduction in the nicotine content of the/smoke, even as little as 15 to 20% is of some value but it is apparent that a larger reduction is needed to afford substantial benefits. p

The specific examples given above are merely illustrative and are not to be construed as limiting the scope of the invention which comprises the treatment of any type of tobacco in any form which is to be used ultimately for smoking purposes by exposure to the recited lower alkyl halides under reaction conditions sufiiciently mild to prevent substantial alteration of the flavor of the product. What is claimed is: 1. Smoking tobacco in a form ready to be smoked and which, during the smoking thereof, produces smoke of substantially reduced nicotine content resulting from the treatment of the tobacco, prior to its being smoked, with a sufficient amount of a dry, gaseous lower alkyl halide alkylating agent selected from the group consisting of methyl and ethyl bromides and chlorides until a substantial proportion of the nicotine in the tobacco chemically reacts with the alkyl halide to form a completely organic nicotine derivative containing a bond between the pyridine nitrogen atom and a carbon atom of the alkyl radical of the alkyla'ting agent and being completely combustible,

said nicotine derivative having smoking properties more favorable than nicotine.

2. Smoking tobacco according to claim L in which the amount of alkylating agent is about stoichiometrically equal to the amount of nicotine in the tobacco.

3. Smoking tobacco according to'claim 2, in which the treatment of the tobacco with the alkylating agent takes place in a closed reaction vessel.

4. The method of substantially reducing the nicotine content of smoke produced from smoking tobacco during the smoking thereof which comprises subjecting the tobacco, prior to its being smoked, at a temperature of about 45 to 50 C. but not over 60 C. to the action of a dry, gaseous lower alkyl halide alkylating agent selected from the group consisting of methyl and ethyl bromides and chlorides until a substantial proportion of the nicotine in the tobacco chemically reacts with the alkyl halide to form a completely organic nicotine derivative containing a bond between the pyridine nitrogen atom and a carbon atom of the alkyl radical of the alkylating agent and being completely combustible, said nicotine derivative having smoking properties more favorable than nicotine.

5. A method according to claim 4, in which the alkylating agent is used in an amount about stoichiometrically equal to the amount of nicotine in the tobacco.

6. A method according to claim 5, in which the tobacco is treated with the alkylating agent in a closed reaction vessel.

References Cited in the file of this patent UNITED STATES PATENTS 685,059 Richards Oct. 22, 1901 1,963,471 Mills June 19, 1934 2,080,179 Merriam et a1 May 11, 1937 2,298,532 Franich Oct. 13, 1942 2,310,538 Musher Feb. 9, 1943 2,429,567 Sowa Oct. 21, 1947 

1. SMOKING TOBACCO IN A FORM READY TO BE SMOKED AND WHICH, DURING THE SMOKING THEREOF, PRODUCES SMOKE OF SUBSTANTIALLY REDUCED NICOTINE CONTENT RESULTING FROM THE TREATMENT OF THE TOBACCO, PRIOR TO ITS BEING SMOKED, WITH A SUFFICIENT AMOUNT OF A DRY, GASEOUS LOWER ALKYL HALIDE ALKYLATING AGENT SELECTED FROM THE GROUP CONSISTING OF METHYL AND ETHYL BROMIDES AND CHLORIDES UNTIL A SUBSTANTIAL PROPORTION OF THE NICOTINE IN THE TOBACCO CHEMICALLY REACTS WITH THE ALKYL HALIDE TO FORM A COMPLETELY ORGANIC NICOTINE DERIVATIVE CONTAINING A BOND BETWEEN THE PYRIDINE NITROGEN ATOM AND A CARBON ATOM OF THE ALKYL RADICAL OF THE ALKYLATING AGENT AND BEING COMPLETELY COMBUSTIBLE, SAID NICOTINE DERIVATIVE HAVING SMOKING PROPERTIES MORE FAVORABLE THAN NICOTINE. 